1. Field of the Invention
The present invention relates generally to oil well running tools. More specifically, the invention relates to a running tool adapted to engage a setting sleeve on a drill pipe or tubing string in a well bore, and specifically to a running tool which allows right hand rotation to be used during well bore operations and to release the setting tool from the setting sleeve.
2. Background of the Invention
Running tools are used for various purposes during well drilling and completion operations. For example, a running tool is typically used to set a liner hanger in a well bore. The running tool is made up in the drill pipe or tubing string between the liner hanger and the drill pipe or tubing string running to the surface. The running tool serves as a link to transmit torque to the liner hanger to place and secure the liner in the well bore. The running tool is then typically manipulated from the surface to effect release of the running tool from the liner hanger. The liner may then optionally be cemented into place in the well bore.
In a typical drill pipe or tubing string, lengths of drill pipe or tubing are connected by tool joints using right hand threads on the drill pipe. These joints are made up using right hand torque and unscrewed or released using left hand torque. Drilling is carried out by right hand or clockwise rotation of the drill string to avoid breaking out or loosening the tool joints making up the pipe string.
In one prior running tool design, connecting threads have been used to engage the running tool with the setting sleeve. In these designs, the running tool is releasable by right hand torque on the pipe string from the surface. However, this design requires holding or maintaining left hand torque on the pipe string while running into the well bore. These designs also require that the liner be set to the left in order to avoid releasing the running tool connecting threads. Because left hand torque is used to set the liner, the possibility exists that tool joints in the drill string can be unscrewed and a joint broken out.
In another prior running tool design, right hand rotation is used to both engage the liner hanger with the running tool and release the running tool from the liner hanger. FIGS. 1a and 1b are sectional views of a prior running tool design shown in a running-in position. The running tool 10 includes a mandrel body 12 having a threaded float nut 70 disposed on its lower end to engage a liner hanger. The running tool also includes a thrusting cap 58 having one or more latch keys 64 disposed thereon which are adapted to engage slots formed on the upper end of the liner hanger. The thrusting cap 58 is selectively engageable to the mandrel body 12 through a hydraulic assembly and a clutch assembly 19 which is engaged in the run-in position. Weight down is defined as the weight of the drill string supported on the running tool and liner hanger. The hydraulic assembly can be actuated to release the thrusting cap 58 from rotational connection with the mandrel body 12 to allow the threaded float nut 70 to be backed out of the liner hanger. The clutch assembly 19 is disengaged when the tool is in the weight down position. A torque nut 82 moves down a threaded surface of the thrusting cap 58 to re-engage the thrusting cap 58 and transmit torque imparted by the mandrel body 12 from the drill string to the thrusting cap 58.
One problem with this design is that the running tool can only be released from the liner hanger in a weight down position. The weight of the drill string causes the clutch assembly, e.g., the torque lock, to disengage from the key 78, thereby allowing relative rotation between the thrusting cap 58 and the float nut 70. This design is therefore limiting in its operation.
Therefore, there exists a need for a running tool which is releasable using right hand torque in any position such as weight down position, neutral position, or weight up position.